Precursors of human sperm and eggs made from stem cells
![reprogrammed human stem cells in an embryoid](https://i0.wp.com/www.sciencenews.org/wp-content/uploads/2014/12/ticker_eggandsperm.jpg?fit=860%2C460&ssl=1)
Some human stem cells in an “embryoid,” glow green indicating that they are making a protein called SOX17. The protein marks cells that may give rise to eggs or sperm.
Walfred Tang, University of Cambridge